Abstract: Calorific values of wastewater plant sludges are best determined using an oxygen bomb calorimeter, an apparatus which is not readily available in many plants. Using a variety of sludges from thirteen municipal wastewater treatment plants in southeastern Wisconsin, an excellent correlation is established between the calorific value and chemical oxygen demand of the sludges. A well-tested recommended procedure for conducting the chemical oxygen demand of wet sludges and semi-dry cakes is also presented.